DTC P0117 Engine Coolant Temperature (ECT) Sensor Circuit Low Voltage. Chevrolet PJJ 2000

For 1990-2009 cars
Engine Controls Components
Engine Data Sensors
OBD II Symbol Description Notice
Powertrain Control Module Connector End Views
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice

### Circuit Description

The Engine Coolant Temperature (ECT) sensor uses a thermistor in order to control the signal voltage to the Powertrain Control Module (PCM). The PCM supplies a voltage on the signal circuit to the sensor. When the engine is cold, the sensor resistance is high, therefore, the ECT signal voltage will be high.

As the engine warms, the sensor resistance becomes less and the voltage drops. At the normal engine operating temperature, the voltage will be between 1.5 and 2.0 volts at the ECT signal terminal.

The ECT sensor controls the following items:

• | The fuel delivery

• | The Torque Converter Clutch (TCC)

• | The Ignition Control (IC)

• | The Evaporative Emission (EVAP) canister purge valve

• | The Idle Air Control (IAC) valve

• | The Electric cooling fan

### Conditions For Running The DTC

The engine run time is greater than 128 seconds.

### Conditions for Setting the DTC

The ECT sensor indicates that the engine coolant temperature is more than 138°C (280°F) for 12.5 seconds.

### Action Taken When the DTC Sets

• | The Malfunction Indicator Lamp (MIL) will illuminate. after two consecutive ignition cycles in which the diagnostic runs with the fault active.

• | The PCM will record the operating conditions at the time that the diagnostic fails. This information will store in the Freeze Frame and Failure Records buffers.

• | A history DTC stores.

• | The coolant fan turns ON.

• | The PCM will default to 20°C (68°F) for the first 60 seconds of the engine run time and then to 92°C (198°F).

### Conditions for Clearing the MIL/DTC

• | The MIL will turn OFF after three consecutive ignition cycles in which the diagnostic runs without a fault.

• | A history DTC will clear after 40 consecutive warm up cycles without a fault.

• | Use a scan tool to clear the DTCs.

### Diagnostic Aids

• | The normal operation temperature of the cooling system is between 90°C (194°F) and 95°C (203°F).

• | Intermittent P0117 is caused by a poor electrical terminal connection.

• | Use the Temperature vs. Resistance table in order to evaluate the possibility of a skewed sensor. Refer to Temperature Versus Resistance .

### Test Description

The numbers below refer to the step numbers on the diagnostic table.

1. This step simulates a DTC P0118. The PCM and the ECT wiring are OK if the PCM senses the change in the ECT sensor signal.

2. Reprogram the replacement PCM and perform the Crankshaft Position System Variation Learn procedure.

#### DTC P0117 - Engine Coolant Temperature (ECT) Circuit - Low Voltage

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the Powertrain On Board Diagnostic (OBD) System Check? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check

2

1. Turn ON the ignition, with the engine OFF.
2. Install a scan tool.

Does the ECT sensor value measure greater than the specified value?

130°C (266°F)

Go to Step 4

Go to Step 3

3

1. Review the Freeze Frame data and record the parameters.
2. Start the engine.
3. Operate the vehicle within the Freeze Frame conditions and Conditions for Running this DTC.

Does the ECT sensor value measure greater than the specified value?

130°C (266°F)

Go to Step 4

Go to Diagnostic Aids

4

1. Turn OFF the ignition.
2. Disconnect the ECT sensor connector.
3. Turn ON the ignition, with the engine OFF.

Does the ECT sensor value measure less than the specified value?

-30°C (-22°F)

Go to Step 6

Go to Step 5

5

1. Turn OFF the ignition.
2. Test the ECT sensor signal circuit for a short to ground.
3. If a problem is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 8

Go to Step 7

6

1. Turn OFF the ignition.
2. Replace the ECT sensor. Refer to Engine Coolant Temperature Sensor Replacement .

Did you complete the replacement?

--

Go to Step 8

--

7

1. Inspect for a poor connection at the PCM.

Important:: The replacement PCM must be programmed and the Crankshaft Position Variation procedure must be performed.

2. If the PCM connections are OK, replace the PCM. Refer to Powertrain Control Module Replacement/Programming and Crankshaft Position System Variation Learn .

Did you complete the replacement?

--

Go to Step 8

--

8

1. Use a scan tool to clear the DTCs.
2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

--

Go to Step 2

System OK